tag:blogger.com,1999:blog-88442016941882690132018-03-08T10:16:11.656-05:00Concrete ToblogganThe storied development of a cutting-edge 300 pound sled.UW Concrete Tobogganhttp://www.blogger.com/profile/16001132998101545193noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8844201694188269013.post-74976279042295366582013-04-09T20:00:00.001-04:002013-04-18T18:42:42.311-04:00SPIRIT THEME (almost) DECIDED!!We have just passed the most point in the realm of spirit. The event that stirs up so much excitement that the spirit engines get roaring, we've decided our theme by a team wide vote, and its a doozy.<br /><br />BUT, the announcement is going to have to wait until we can register it. Then we'll announce it to the world. Until then, it could be anything from the YMCA to the secret service, and all the superhero action in between.<br /><br />We are so pumped for this theme its incredible, and it's going to bring the manliest, cheesiest songs back in style like its our god given purpose to!<br /><br />Fraser<br />Spirit Captain 2014Fraser Lordhttps://plus.google.com/111511766167238591705noreply@blogger.com1tag:blogger.com,1999:blog-8844201694188269013.post-63009235147577767982013-03-31T02:00:00.000-04:002013-04-18T18:41:55.689-04:00Let's talk Chrome-Moly - Part 2<h2>Part 2 - Martyr DOM</h2>In <a href="http://uwconcretetoboggan.blogspot.ca/2013/03/lets-talk-chrome-moly-part-1.html">Part 1</a> we talked about the strength differences between 1020 DOM and Chrome-Moly, two materials commonly used in the construction of roll cages. We concluded that the differences were not sufficient enough to justify the price alone, but Chrome-Moly still has a chance here.<br /><br />In this part, we're going to go through some fabrication differences as well as comments from people who have worked with both materials.<br /><br /><h3><b>Only as strong as your weakest link.</b></h3>Steel sheets are formed and rolled in highly consistent, standardized conditions. Your welds are not. Generally speaking, the quality of the weld will determine the strength of the frame. Tubes (which are what most racing roll cages are made out of) are great at handling axial forces, but those axial forces must be transferred and redirected at welded joints. You have a ton of forces coming from different directions at a joints, as well as stress from rapid expansion and contraction during welding at joints.<br /><br />In short, bad welding creates weak points. Choosing an easy to weld material reduces fabrication cost, reduces wear on welding equipment, and increases safety by decreasing probability of error. <br /><br /><a name='more'></a><h3><b>How easy are 4130 and 1020 to weld exactly?</b></h3><i>Chrome-Moly isn't easy to weld. </i>Sources vary on how easy it can be, suggesting everything from being able to weld it straight (due to purity) to requiring preparation. Erring on the safe side, I'll outline some hiccups to welding it:<br /><ul><li><a href="http://members.eaa.org/home/homebuilders/building/welded/4Welding%20-%20It%27s%20Not%20Black%20Magic.html">Chrome-Moly doesn't take thermal shock well.</a> That means stresses and cracks from thermal expansion and contraction are more prevalent than other lower-carbon steels (like 1020 DOM, which has 0.10% lower Carbon per unit wt)</li><ul><li>This means it has to be heated slowly. And not only that, the frame around the weld must be preheated so it doesn't suck heat too fast from the weld.</li><li>It also has to be cooled very slowly. Air cooling is too fast, and it is preferred to play with the weld using a torch to cool it to red.</li></ul><li>From the same source, Chrome-Moly is generally TIG welded because MIG welding injects heat too fast.</li><ul><li><a href="http://www.used-robots.com/articles.php?tag=2986">TIG welding usually requires more skill than MIG welding</a></li><li>TIG requires more set up</li><li>TIG is more expensive, basically</li></ul><li>It follows that 1020 DOM steel <a href="http://www.staticmoto.com/R&amp;D.html">can be MIG welded</a> faster, with more tolerance for error, and less preparation.</li></ul>For general 4130 welding guidelines, see: <a href="http://www.arc-zone.com/blog/joewelder/2009/01/08/metal-of-the-month-chromoly/">http://www.arc-zone.com/blog/joewelder/2009/01/08/metal-of-the-month-chromoly/</a>. For specific welding controls, see: <a href="http://millerwelds.com/resources/articles/Best-Practices-for-GTA-Welding-of-4130-Chrome-Moly-Tubing">http://millerwelds.com/resources/articles/Best-Practices-for-GTA-Welding-of-4130-Chrome-Moly-Tubing</a> <br /><br />This round goes to 1020 DOM again. <br /><br /><h3><b>Additional Comments</b></h3>We are by far not the first team to have a decision like this. Here are some other comments from welding forums, buggy enthusiasts and small aircraft enthusiasts:<br /><blockquote>"After lengthy research I concluded that to make a worthwhile 4130 chromoly frame I would need to pre-treat my materials, TIG weld everything, then properly stress-relieve the weld areas (oven heat treatment, normalizing, etc). Moreover if I or my customers wanted to modify, add-to, or repair a frame, I/they would have to have access to all of this equipment... Most fabricators agree 4130 chromoly is not much stronger unless appropriately treated... 1020 DOM is easy to work with: you the customer can modify and/or repair the frame with a MIG welder. No special equipment or processes needed."</blockquote><a href="http://www.practicalmachinist.com/vb/general-archive/4130-welded-frame-anyone-82716/">http://www.practicalmachinist.com/vb/general-archive/4130-welded-frame-anyone-82716/</a><br /><blockquote>"1020 DOM is usually safer for a roll cage because of its greater elongation properties. The 1020 will continue to bend after the 4130 has ruptured. Sometimes 4130 is used because it is processed in a more controlled enjoinment and certified for aircraft use compared to commercial grade 1020... If you don't heat treat for greater strength, then just use 1020 DOM to reduce costs, not just in material but tools wear out faster with 4130."</blockquote><a href="http://www.practicalmachinist.com/vb/general-archive/4130-welded-frame-anyone-82716/">http://www.practicalmachinist.com/vb/general-archive/4130-welded-frame-anyone-82716/</a><br /><br /><h3><b>Conclusions</b></h3>Despite all the flaws of Chrome-Moly, why do people&nbsp; use it? That's a good question, and based on my brief research, the conclusion seems to be that 4130 Chrome-Moly steel is: <br /><ul><li>able to achieve higher strength than 1020 DOM with heat treatment</li><ul><li>it does require work, however if strength to weight is more critical than factors such as cost, time and ease of fabrication, then nobody will question your priorities</li></ul><li>available in a purer form than 1020 DOM (created in more tightly controlled conditions)</li></ul>Even with all my marks against it, I cannot deny that in the right hands (such as those constructing airplanes) <b>Chrome-Moly steel is a better choice for highly weight-critical applications</b>. But those choosing it just to say they have exotic aircraft steel in their project should beware: cheaper solutions can work just as well and be less of a pain. <b>1020 DOM is a better choice for strength-to-weight vs. cost vs. ease of construction.</b>Billy E16http://www.blogger.com/profile/17109515180135652590noreply@blogger.com0tag:blogger.com,1999:blog-8844201694188269013.post-47451382718557683992013-03-27T19:44:00.005-04:002013-04-18T18:42:08.072-04:00Let's talk Chrome-Moly - Part 1<h2>Part 1 - Holy Moly </h2>No, Chrome-Moly is not a web browser, nor is it a middle name after a complicated marriage.<br /><br />Chrome-Moly, or SAE 4130 grade steel, is a type of steel that contains chromium and molybdenum alloying elements. This alloy has a better strength to weight ratio than 1020 DOM steel (which we'll talk about later). For this reason, it's used to create structures where weight is very critical, such as high-end bicycle frames, roll cages for race cars, and fuselages on small aircraft.<br /><br />Chrome-Moly is one of the possible materials we can be using for our frame, because weight is an issue in the competition. In this series of articles, let's do a basic comparison between Chrome-Moly and the standard 1020 DOM (Drawn over Mandrel) steel. Both chrome-moly and 1020 DOM are <a href="http://books.google.ca/books?id=rSjoF5gxPscC&amp;pg=PT290&amp;lpg=PT290&amp;dq=chrome-moly+dom&amp;source=bl&amp;ots=hsZ5-9Ppuu&amp;sig=vEFDjy-wgZlSlk1COk5U0Kzw8pA&amp;hl=en&amp;sa=X&amp;ei=_HhTUcizA-X4yQGgx4HwCg&amp;ved=0CDwQ6AEwAQ">typically used in the manufacture of roll cages</a>, which makes them a good starting point for the frame.<br /><br /><a name='more'></a><h3><b>General Pros/Cons of Chrome-Moly:</b></h3><ul><li>Pro: Higher strength-to-weight than 1020 DOM</li><li>Con: Expensive (around 1.5 times more expensive per unit length) <a href="http://www.stockcarsteel.com/4130-chrome-moly/4130-chrome-moly-round-tube">source 1</a> <a href="http://www.stockcarsteel.com/dom-steel-tube-drawn-over-mandrel/">source 2</a></li><li>Con: Must be heat treated to achieve extra strength</li><li>Con: Harder to weld than 1020 DOM (must be heated before welding)</li><li>Con: Less flexibility than 1020 DOM</li></ul><br />With all those cons, you'd think that Chrome-Moly is out of the picture, but it depends on how much you value weight. Chrome-Moly's typical application is to <a href="http://www.arc-zone.com/blog/joewelder/2009/01/08/metal-of-the-month-chromoly/">reduce the weight of a structure while maintaining the same strength</a> as if you had built it out of 1020 steel.<br /><br />The comparison boils down to strength-to-weight vs. cost vs. ease of construction. <br /><br /><h3><b>How strong is chrome-moly exactly?</b></h3>The tensile strength of 1020 DOM tube: <a href="http://www.staticmoto.com/R&amp;D.html">70ksi – 80ksi</a> (480-550 MPa)<br />And now a normalized 4130 tube: <a href="http://www.staticmoto.com/R&amp;D.html">90ksi – 93ksi</a> (620 - 840 MPa, this is after heat treating).<br />So 4130 is about 25% stronger. That's a bit disappointing. Where did all that godly strength go?<br />Maybe it's much lighter. Well, no, <a href="http://www.millerwelds.com/resources/articles/Best-Practices-for-GTA-Welding-of-4130-Chrome-Moly-Tubing">chrome-moly is the same weight as regular steel</a> (491 lb/ft3, 7865 kg/m3).<br /><br />So it's 25% stronger-to-weight for 50% more cost. Hmm...<br /><br />But wait! It turns out that you can achieve up to 130ksi (895 MPa), but it requires a heat treating process of <a href="http://www.pirate4x4.com/forum/general-4x4-discussion/84559-chromoly-welding.html">normalizing at 1200°F (650°C), slow cooling, heating the chassis to 1550°F (845°C), water quenching, and then a 1000°F (540°C) temper</a>. With time and equipment, we can create a super-strong chassis that makes the most out of the cost, but is it worth it?<br /><br />This round goes to 1020 DOM for now. <b>&nbsp;</b><br /><br /><b>In Part 2</b> we'll talk overview fabrication: the ease-of-construction part of our comparison! We'll also talk about typical shapes and other welding details.<br /><br /><b>Update 1:</b> Added SI units because we're Canadian!Billy E16http://www.blogger.com/profile/17109515180135652590noreply@blogger.com0tag:blogger.com,1999:blog-8844201694188269013.post-35566969095738477762013-03-27T12:01:00.004-04:002013-04-18T18:42:26.446-04:00Welcome to the Blog!Welcome to the University of Waterloo Concrete Toboggan team's official blog! Here you'll see our latest updates as we construct a 300 pound concrete and steel toboggan to compete in the 2014 Great Northern Concrete Toboggan Race, hosted in London, Ontario.<br /><br />For our first post, here are some of the skilled students we have on board who will be contributing technical knowledge to this blog:<br /><br />Hi! I'm <b>Billy Eakkachaichanvet</b>, the Business Logistics Lead. My role is to execute the business side of the team, such as managing sponsor relations, budgeting and coordinating marketing elements such as this website. I joined the team in the 2012 year because I found the idea of using my studies in civil engineering (i.e. reinforced concrete) in a competitive application (a race) intriguing.Billy E16http://www.blogger.com/profile/17109515180135652590noreply@blogger.com4